The oncoprotein mdm2 (murine double minutes) was originally isolated through its ability to transform mouse BALB/c fibroblast cells (Fakharzadeh, et al., 1991). In the transformed cells, the mdm2 gene is often amplified and exists as a double minute chromosome. The mdm2 gene encodes a protein of 491 amino acids and contains all the domains necessary for being a transcription factor. It has a consensus nuclear translocation signal, two zinc binding domains and acidic and basic domains (Brown, et al., 1993). The mdm2 gene is located on human chromosome 12q13-14 and is often seen to be co-amplified with the CDK4 gene (a cyclin dependent kinase gene which is located within the same region) in human malignant gliomas (He, et al., 1994, Reifenberger, et al., 1995). Amplification of the mdm2 gene has also been found in a variety of human sarcomas (Ollner, et al., 1992; Ladanyl, et al., 1993; Khatib, et al., 1993). Amplification of the mdm2 gene is, however, not universal; many tumours, including some types of leukaemia, were found to have no amplification of the mdm2 gene (Ridge, et al., 1994). Nevertheless, abnormal expression of the mdm2 gene has been found in many types of human tumour. Abnormal expression of mdm2 has been reported in chronic lymphocytic leukaemia (Watanbe, et al., 1994; Huang, et al., 1994). Elevated mdm2 expression was also found in Hodgkin's and non-Hodgkin's lymphomas at both mRNA and protein levels (Chllosl, et al., 1994, Finnegan, et al., 1994). High levels of expression of the mdm2 gene have been linked to a poor response to chemotherapy and short survival in haematological malignancies (Quesnel, et al., 1994).